Israel never discusses "core issues". The reason for this is that every single core issue will require a concession on the part of Israel. More than one of these concessions are considered "deal breakers" by Israel and the ones that are not considered deal breakers are still very important and still require an Israeli concession. Not only won't Israel talk about core issues, they won't even talk about talking about core issues.
Yemen's Houthi rebels commit to peace plan in letter to UN chief, BBC reports (Haaretz)